JPS62123317A - Air intake detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable accurate measurement of amount of air regardless of rotational speed, by sampling an output of a thermal type sensor at each angle of rotation of an internal combustion engine. CONSTITUTION:A throttle chamber of an internal combustion engine is provided with an air path and an electrically heat-generating body 24 is provided to detect the flow rate of air. A cyclic electric signal 24A varying with air flow velocity is fetched from the heat-generating body 24 and is inputted into a control circuit 70. An instantaneously air flow are qa changes correspondingly to variation in the angle of crank and the change has a fixed pulsating cycle which corresponds to the angle of crank. An output of the heat-generating body 24, namely, the amount of air varies depending on the angle of crank. But, as to the intake timing, the instantaneous amount of air qa1...qam is taken in from the heat-generating body 24 at each specified angles t1...tm as angle of crank. The amount of air qa1...qam thus taken in is subjected to a A/D conversion 102 and the results are stored into respective RAMs 112. In other words, after being digitized, it is stored sequentially into specified (m) pieces of registers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake air amount detection device for an internal combustion engine.

[Conventional technology]

2. Description of the Related Art It is conventionally known to detect the amount of air taken into an internal combustion engine using a thermal sensor, as disclosed in Japanese Patent Application Laid-open No. 123462/1983.

It is also known to use a digital method to process the output of this thermal sensor, as disclosed in Japanese Patent Laid-Open No. 77732/1983.

[Problem that the invention seeks to solve]

By the way, the technique described in Japanese Unexamined Patent Publication No. 50-77732 is a system using wired logic, and in this case, the output of the thermal sensor is constantly processed by an analog-to-digital converter.

On the other hand, recently, attempts have been made to install a microcomputer as a central control device for an internal combustion engine. and,
This feature is that many other processes can be performed in addition to thermal sensor processing.

For this reason, many analog signals are selected by a multiplexer and transmitted to an analog-to-digital converter for processing.

When the multiplexer converts the analog output of the thermal sensor into a digital output, the output of the thermal sensor is sampled at a constant sampling period.

However, since the internal combustion engine repeats the combustion cycle, the thermal sensor output also pulsates according to this cycle, and the period of this pulsation depends on changes in the rotational speed.

For this reason, even though there is a change in the pulsation period, sampling is performed at a constant sampling period, so that it is not possible to measure the amount of air taking pulsation into consideration.

In addition, since a microcomputer is used, the calculation cycle for thermal sensor output processing is determined based on the short pulsation cycle, that is, high-speed operation, so accurate calculations are possible even if the calculation cycle is long during low-speed operation. Despite the fact that it is possible to perform
There is a problem of inefficient use of microcomputers.

[Means for solving problems]

In order to eliminate the above problems, the present invention provides: (a) a thermal sensor provided in the intake air passage; (b) an analog-to-digital converter that converts the analog signal of the thermal sensor into a digital signal; (c) ). An intake air amount detection device for an internal combustion engine, comprising a control stage that samples an analog signal from the thermal sensor at every predetermined rotation angle of the internal combustion engine and transmits it to the analog-to-digital converter to perform analog-to-digital conversion. It is composed of

[Effect]

According to the present invention, since the output of the thermal sensor is sampled at each rotation angle of the internal combustion engine, it is possible to perform sampling while following changes in the pulsation period from low-speed operation to high-speed operation.

〔Example〕

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

In FIG. 6, a control device for the entire engine system is shown in FIG. 1. Intake air passes through an air cleaner 2, a throttle chamber 4, and an intake pipe 6, and is supplied to a cylinder 8. The gas burned in the cylinder 8 passes through the exhaust pipe 10 from the cylinder 5 and is discharged into the atmosphere.

The throttle chamber 4 is provided with an injector 12 for injecting fuel.
The fuel ejected from the throttle chamber 4 is atomized in the air passage of the throttle chamber 4 and mixed with the intake air to form a mixture, and this mixture passes through the intake pipe 6 and when the intake valve 20 is opened.
It is supplied to the combustion chamber of cylinder 8.

Throttle valves 14 and 16 are provided near the outlet of the injector 12. The throttle valve 14 is configured to be mechanically interlocked with the accelerator pedal and is driven by the driver.

On the other hand, the throttle valve 16 is arranged so as to be driven by the diaphragm 18, and is fully closed when the air flow rate is small.As the air flow rate increases, the negative pressure on the diaphragm 18 increases, so that the throttle valve 16 It begins to open and suppresses the increase in inhalation resistance.

An air passage 22 is provided upstream of the throttle valve 14, 16 of the throttle chamber 4, and an electric heating element 24 constituting an air flow rate detector is disposed in this air passage 22. A periodic electrical signal is extracted that changes in accordance with the air flow velocity, which is determined from the relationship with the amount of heat transfer. heating element 2
4 is provided in the air passage 22, so the cylinder 8
It is protected from high-temperature gases generated during a backfire, and is also protected from contamination by dust in the intake air. The outlet of the air passage 22 is opened near the narrowest part of the venturi, and the inlet thereof is opened on the upstream side of the venturi.

The fuel supplied to the injector 12 is supplied to the fuel tank 30
From, fuel pump 32. The fuel is supplied to a fuel pressure regulator 38 via a fuel damper 34 and a filter 36. On the other hand, pressurized fuel is supplied from the fuel pressure regulator 38 to the injector 12 via a pipe 40, and the difference between the pressure in the intake pipe 6 through which fuel is injected from the injector 12 and the fuel amount pressure to the injector 12 is always constant. As such, fuel is returned from the fuel pressure regulator 38 to the fuel tank 30 via the return pipe 42.

The air-fuel mixture taken in from the intake valve 20 is compressed by the piston 50 and combusted by the spark from the ignition plug 52.
This combustion is converted into kinetic energy. The cylinder 8 is cooled by cooling water 54, and the temperature of this cooling water is measured by a water temperature sensor 56, and this measured value is used as the engine temperature.

A high voltage is supplied to the spark plug 52 from an ignition coil 58 in accordance with the ignition timing.

In addition, the crankshaft (not shown) is attached at each reference crank angle and at a certain angle (for example, 0.5
A crank angle sensor is provided that outputs a reference angle signal and a position signal for each angle (degrees).

The output 60 of the crank angle sensor, the output 56A of the water temperature sensor 56, and the electrical signal 24A from the heating element 24 are input to a control circuit 70 consisting of a microcomputer or the like.
The control circuit 70 performs arithmetic processing, and the output of the control circuit 70 drives the injector 12 and the ignition coil 58.

The operation of the engine described above will be explained with reference to FIG. 2. FIG. 2A shows the injection timing of fuel from an injector in a four-cylinder engine. The horizontal axis is the rotation angle of the engine's crankshaft, and as is clear from Figure 6, which shows the intake stroke of each cylinder with hatching, there is an intake stroke for every 180 degrees of the crank angle, and from 0 degrees to]
, between 80 degrees is the first cylinder, between 180 degrees and 360 degrees is the third cylinder, between 360 degrees and 540 degrees is the fourth cylinder, and between 540 degrees and 720 degrees is the second cylinder. In Figure 2A,
A! to A4 indicate fuel injection time, and Pz to P4 indicate ignition timing.

Figure 2B shows the instantaneous air flow rate q relative to the crank angle rotation angle θ.
& is shown. The instantaneous air flow rate qa changes in response to changes in the crank angle, and the changes have a constant pulsation period. This period corresponds to the crank angle θ.

Next, the control circuit 7o will be explained based on FIG. Third
The figure shows specific blocks of the control circuit 70, and the input signals in the figure can be roughly classified into three types. That is, first, the heating element 24 detects the amount of intake air.
There are analog inputs sent from the output 24A of the engine cooling water, the output 56A of the sensor 56 that detects engine cooling water, and the like.

These analog inputs are input to a multiplexer (hereinafter referred to as MPX) 100, and the output of each sensor is selected in a time-sharing manner and sent to an analog-to-digital converter (hereinafter referred to as ADC) 102, where it is converted into a digital value. Ru. Second on.

The information is input as an off signal, and this is, for example, a signal θTH indicating the fully open state of the throttle valve, which is the signal 1 sent from the switch 104 that operates in conjunction with the throttle valve.
There is 04A. This signal can be handled as a 1-bit digital signal.

Furthermore, the third possible input signal is a signal input as a pulse train, such as a reference crank angle signal (hereinafter referred to as CRP).
It is written as ) and a position pulse signal (hereinafter referred to as CPP), and these signals are sent from the crank angle sensor 106.

CRP is output every 180 degrees of crank angle in the case of 4 cylinders, every 120 degrees in the case of 6 cylinders, and every 90 degrees in the case of 8 cylinders. CPP is output, for example, every 0.5 degrees of crank angle.

CPU 108 is a processing central unit that performs digital arithmetic processing, ROM 110 is a storage element for storing control programs and fixed data, and RAM 11.2 is a readable and writable storage element. The input/output interface circuit 114 receives input signals from the ADC 102 and the sensors 104 and 106, and sends the signals to the CPU 1o8. Also, CPU
The signal from 2O5 is sent to the injector 12 and ignition coil 58 as signals INJ and IGN. In addition.

A voltage is applied from the power supply terminal 116 to each circuit and element constituting the control circuit 70, but their illustration is omitted in the drawing. Further, the injector 12 and the ignition coil 58 are each provided with an electromagnetic coil for driving the valve and a primary coil for accumulating electromagnetic energy, one end of which is connected to the power terminal 116,
The other end is connected to the input/output interface circuit 114,
The current flowing into the injector 12 and the ignition coil 58 is controlled.

The amount of fuel injected by the injector 12 described above is controlled by the control circuit 14 based on the amount of incoming air detected by the heating element 24. In particular, as described above, the instantaneous air flow rate q & varies depending on the crank angle θ, and it is necessary to detect the air amount without being affected by this variation.

Therefore, the present invention performs the following processing.

FIG. 4 shows the timing at which the constant angle flow rate is taken into the RAM 112.

In FIG. 4, the output of the heating element 24, that is, the amount of air, fluctuates depending on the crank angle θ, as in FIG.
Instantaneous air amount 'T from the heating element 24 at tz...t.
&1 tq a! . . . It takes in q&+s.

Then, the instantaneous amount of air taken in is 'T&1+q&2・
...qas is analog-digital converted and digitized by the ADC 102, and then stored in the RAM 112.
is stored in

FIG. 5 shows the contents stored in the register in the RAM 112, and shows the instantaneous air it qa taken in at a predetermined angle.
bqax...qas are digitized and sequentially stored in m predetermined registers.

〔Effect of the invention〕

As described above, according to the present invention, since the amount of air is taken in at each predetermined rotation angle, the combustion cycle is
Single sampling and analog-to-digital conversion allow accurate air volume measurement, and sampling and digitization are performed a predetermined number of times per fuel cycle regardless of rotation speed, eliminating unnecessary calculations during low-speed operation. This eliminates the need to perform multiple steps, thereby increasing the efficiency of using the microcomputer.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the control device for the entire engine system, Figure 2 is an explanatory diagram showing the engine process and fuel injection timing, Figure 3 is a block diagram of the engine control circuit, and Figure 4 is a constant angle flow rate. FIG. 5 is an explanatory diagram showing the capture timing, and FIG. 5 is an explanatory diagram showing the storage contents of the RAM. 70... Control circuit, 108... CPU, 110...
・ROM, 112... RAM, 114... Input/output interface circuit.

Claims (1)

[Claims] 1. (a) A thermal sensor provided in the intake air passage; (b)
, an analog-to-digital converter that converts the analog signal of the thermal sensor into a digital signal; (c) sampling the analog signal of the thermal sensor at every predetermined rotation angle of the internal combustion engine and converting the analog signal to the analog-to-digital converter; An intake air amount detection device for an internal combustion engine comprising a control stage for transmitting data and performing analog-to-digital conversion.